Icahn holds stakes of roughly 10 percent in both the Oshkosh, Wisconsin-based company and rival Navistar International Corp (NAV.N), and said in December he would like to see the companies merge. He has also called on Oshkosh to consider selling its JLG aerial lift business and pay down debt.

Oshkosh, meanwhile, has said its executives have met Icahn multiple times and he has not proposed "substantive ideas" that would benefit all shareholders.

The maker of fire trucks, cement mixers and military vehicles contends it had no contact with Icahn prior to his June disclosure in a filing with the U.S. Securities and Exchange Commission that he had a 9.5 percent stake in Oshkosh.

About 300 people, mostly Oshkosh retirees, typically attend the company's annual meetings, according to Oshkosh officials. This year's meeting gets underway at 8 a.m. Central time (1400 GMT) at an aviation museum in Oshkosh.

Oshkosh shares have fallen about 32 percent over the past year, while the broad Standard & Poor's 500 index .SPX is up 3 percent. Navistar has declined 30 percent.

Icahn has nominated a slate of six directors to Oshkosh's 13-member board. They include three staffers of his Icahn Enterprises investment firm, Samuel Merksamer, Vincent Intrieri and Daniel Ninivaggi; chief executive Jose Maria Alapont of Icahn-backed Federal-Mogul Corp (FDML.O), consultant Marc Gustafson and former Central Intelligence Agency executive director A.B. Krongard.

One of three major proxy advisory firms, Institutional Shareholder Services, this month backed three of those nominees, Alapont, Krongard and Merksamer. Two others, Glass Lewis & Co and Egan-Jones Proxy Service backed the existing Oshkosh board.

"Mr. Icahn has not demonstrated that he has a plan or a team that can lead your company and deliver value to all Oshkosh shareholders," Oshkosh CEO Charles Szews and Chairman Richard Donnelly wrote in a letter to shareholders earlier this month.

Icahn has criticized the company's management as being thin, heavier on sales and marketing executives than people with manufacturing experience, and notes Oshkosh shares lost 39 percent of their value in 2011, while Icahn's funds gained 15 percent.

Annual shareholder meetings are typically sleepy affairs, but can turn raucous when investors launch concerted campaigns against management.

In 2009, the management of Massachusetts biotechnology company Biogen Idec Inc (BIIB.O) also fought a proxy battle with Icahn and called a three-hour hiatus of the meeting as shareholders were lobbied. The move prompted then-Icahn-lieutenant Alexander Denner to complain shareholders were being ignored, shouting, "This is not North Korea!"

Icahn has sold most of his holdings in Biogen after a spectacular run-up in company's stock after it hired a new CEO, restructured and had positive data from a clinical trial of an experimental multiple sclerosis drug.

Icahn has found a warmer welcome for his approach to Oshkosh rival Navistar.

The Warrensville, Illinois-based company agreed in November to phase out its staggered board structure that allowed directors to serve for overlapping three-year terms in favor of one-year terms for all 10 members of the board. In return, Icahn agreed not to nominate his own slate.

Oshkosh directors already stand for one-year terms.

Navistar CEO Dan Ustian told Reuters in December that he believed there could be a rationale for merging the companies and said he had listened to Icahn's ideas, but would not give him special treatment.

"I don't see that really it's any different than any other shareholder that wants a return," Ustian said of Icahn. "He's got 10 percent so we have to pay attention to him, but it's no different than anyone else. If we give them a return, they'll be happy with it."

(Reporting By Scott Malone; editing by Andre Grenon)

• A Permanent Economic Emergency